Mercury-tube switch



June 7, 1927. V 1,631,713

H. E. WARREN MERCURY TUBE SWITCH Filed Sept. 2l, 1923 Inventor: Henry EWarren, by His Attorney Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

HENRY E. W/ABREN, OF ASHLAND, MASSACHUSETTS, ASSIGNOR TO WARREN CLOCK COMPANY, OF ASHLAND, MASSACHUSETTS, A CORPORATION OF MAINE.

MERCURY-TUBE SWITCH.

Application led September 21, 1923. Serial No. 664,098.

between mercury contacts when the circuit is opened. Other advantages of my invention will appear as the description proceeds. In my United States Letters Patent No. 1,144,973, I have described a mercury tube switch wherein the surface of the tube upon which the mercury moves is roughened to decrease the friction between the mercury and the tube for the purpose of obtaining a more sensitive switch than the ordinary type in which the cont-acting surface of the tube is smooth, The reasons for this phenomenon are fully explained in the patent referred to above..l My present invention utilizes the same phenomenon in combination with other features to obtain an improved type of controller for electric circuits. The features of my invention which I believe to be novel and patentable are pointed out in the claims appended hereto. A preferred embodiment of my invention will now be described in connection with the accompanying drawing in which Figs. 1, 2 and 3 represent dierent operating positions of a mercury tube switch incorporating my invention and Fig. 4, a cross sectionof the tube taken on line 4 4 of Fig. 1.

Referring to the drawings in which like parts are designated by like reference characters throughout, I have illustrated a mercury tube/switch comprising an inner tube 10 containin a quantlty of mercury 11 and an outer tu e 12J enclosin the former -in the manner indicated, toget er with suitable electrodes 13 and 14 sealed into the outer tube near the center and one end respectively. The inner tube is made of some refractory material rwhich is not in the 'least apt to contaminate the mercury under any conditions. I prefer to use for this purpose a glass tube which is free from lead and I find the so-called pyrex glass suitable for this. purpose. This tube ismade either with Y. a hole near its center through which the also lto fit better the corresponding end of the enveloping tube 12. The inner surface of tube 10 is roughened as, for example, by grinding. Chemical action, such as etching, may also be used to roughen the interior of the tube 'and the degree-of roughening may be varied as desirable to obtain dierent operating characteristics, as will be apparent from the description which follows.

The outer tube 12 may be made of any kind of glass or other suitable material which can be easily manipulated and which will form a perfect seal with the electrodes 13 and 14. Inasmuch as it never comes in contact with the mercury where the arc is broken, this outer envelope 12 need not be free from lead. I find that the ordinary lead soda glass is entirely suitable for this outer tube. A chamber 16 is provided beyond one end of tube 10 in which chamber a portion of the mercury will remain whenv the tube is in use. The enveloping tube 12 is preferably not roughened on the inside, consequently that portion of the mercury contained in chamber 16 will adhere strongly to the inner surface of tube 12 and when the tube is nearly level, owing to the fact of the adhesion of the mercury in chamber 16 and the non-adhesion of the mercury in the roughened tube 10, and also to the effect of the dam constituted at 19 by the end of the inner tube 10 adjacent the chamber 16, the mercury will break as indicated in Figs. 2 and 3 when the tube is tilted slightly in a counter-clockwise direction in such a manner as to cause the arc to be wholly contained within the t-.ube and this, by the suddenness and very great length of thebreak,fwill minimize the generatlon of heat by the current. The outer and inner tubes are suitably secured inthe relation shown as for example by a small spring steel wedge 20 shown in Fig. 4

It will be understood thatthe electric circuit controlled by this type of switch is connected 'in series with electrodes 13 and 14 so that when the,A tube is in the position shown in Fig. 1, the circuit will be closed and when in position shown in Fig. 3, the circuit will be open. It will be noted with this construction that no arcing takes place at the surface of the electrodes, but always between masses of mercury. he electrode should of course be made of some material which will not pollute the mercury. I find gen or other suitable platinum is particularly well suited; also steel, althou if steel is used, 1t should be either-welde to some other material which can be fused into the glass, 'or else, alloyed with nickel and covered with copper when the seal is made. The covering of the copper should be removed inside the sea'l because otherwise, it would mix with the mercury and interfere with its mobility. It is of course necessary that the mercury should be of the greatest purity in this contactor. The interior atmosphere may be of hydrogas or the air may be exhausted if the current lto be broken is low.

The operation of the Ltube is more fully explained as follows: In Fig. 1 the tube has a slight tilt in a clockwise direction so as to close the circuit between the electrodes. This tilt, due to the anti-friction action of the roughened tube with mercury, need not be more than one-half degree from a true horizontal position. The heavy dotted line 17 may be taken as a true horizontal referenceE line and the lightly dotted line 18 as the axis of the tube. In position Fig. 1, the circuit is closed by the mass of mercury between the electrodes. The tube may contain suiiicient mercury to completely lill up the tube between electrodes 13 and 14 when the tube is tilted to a vertical position in a clockwise direction so that the degree of tilt, although it need be very small, is quite immaterial and therel is no danger of opening the circuit as is often the case with previous arrangements should the tube be tilted too far in a circuit closing direction.

In Fig. 2, the tube is brought back to substantially a true horizontal position so that the mercury Hows to the left. The condition of the mercury as shown in Fig. 2 is that which will occur when the tube is being moved from the circuit closing position of Fig. 1 to the open circuit position of Fig.l 3. Due to the difference in the adhesion of the mercury on the rough interior surface of tube l0 and the smooth interior surface of chamber 16 and also due to the dam effect at 19, the mercury is drawn out in the form illustrated with a long thin stream in that portion of the tube betweenl the electrodes with a greater amount of mercury surrounding the electrodes themselves. Due to the surface tension of the mercury, this stream will be stretched out, so to speak, until a sudden break will occur at the thinnest point,'mercury flowing both ways therefrom at a rapid rate bringing the mercury to the condition shown in Fig. 3 which illustrates the tube at the end of the open circuiting movement. Not 'only does-this provide a quick break and a long arcing space,'but the arc is entirely between mercury contacts, consequently no burning and wearing away of the electrodes will ever occur and the mercury will not become contaminated by chemical action which might otherwise be produced if the arc was allowed to play on the electrode. Furthermore, the resistance of mercury being somewhat like six times that of copper, the drawing out of the mercury into` a long, thin stream just before the circuit is opened, acts to some extent as anI adjustable resistance in decreasing the current strength. Byl suitably proportioning the dimensions of the tube a considerable current at a considerable voltage may be con- `trolled by this simple circuit breaker. action of the tubes can be modified by modifying the dimensions and degree of roughness of the tube and certain portions may be roughened more than others. The switch is very sensitive, requiring not more than one degree of change in position between its open circuit and closed l tion whereas the ordinary mercuryA tube kswitch requires from ten to twenty degrees tilt between these positions. The tilt illustrated in the drawings is exaggerated for the sake of clearness and is more than is necessary although any greater amount of tilt in either direction is permissible and will lnot aflect the conditions of the circuit. Due to the fact that a mass'of mercury'tends tocling together due to surface tension, amuch larger stream of mercury will be available between the electrodes at the instant the cir-v cuit is closed than whenit is open, cnsequently,

the circuit is quickly and positively closed when the tube is tilted to a circuitclosing position.

Although I have shown but a single modification of my invention, it will be evident to those skilled in the art that various changes may be made therein for example, both ends of the tube shown might be made like the right hand end to provide a double throw, a single pole circuitbreaker. I do not consider the dam 19 essential but preferable to obtain the best results.

' I n accordance with the provisions of the patent statutes, I have described the principle of operation of invention, together The with the apparatus which I now consider to represent the best embodiment thereof; but "I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried outby other means'.

What I claim as new and desire to secure by Letters Patent of the United` States, is:

, l. .An electric circuit controller comprising a tubular sealed chamber of insulating material, a pair of electrodes vsealed into said chamber, so as to provide considerable arcing space between said electrodes, the interior surface of the chamber closely adjacent one electrode being smooth and the interior surface between the electrodes being roughened and a conducting fluid such as mercury'y contained within lsaid chamber in so that the circuit therein is broken by Leanne suicient quantity to electrically connect said electrodes when the chamber` is -in one position, the circuit controller being constructld t e separation of the mercury over the roughened surface of said chamber when tilted toward the open position. f

2. A mercury tube circuit controller comprisingY a sealed tubular chamber of insulating material, two electrodes sealed into said chamber, so as to provide considerable arcing lspace between saidelectr'odes lengthwise of the chamber, the interior of the chamber between the `electrodes being roughened and the interior of the chamber closely adjacent one electrode being smooth, a low dam between said electrodes, and suilicient mercury in said chamber tocover said dam and connect said electrodes when the tube is in one position, the circuit vcontroller being constructed so that the circuit therein is broken by the separation'of the mercury over the roug tilted toward the open-position.

3. An electric circuit controller comprising a sealed glass cylindrical chamber, having an enlarged portion rat one end, said enlarged portion having a smooth interior surface and substantially the remainder of the interior of said chamber being roughened, an electrode sealed into the enlarged portion of said chamber, an electrode sealed into said chamber intermediate its ends so f as "to provide a. considerable arcing space be'- tween said electrodes and a fluid conductor such as mercury contained within said chamber of sufficientquantity to connect said electrodes whenthe chamber is in one position, thecircuit controller being constructed so that the circuit therein is broken by theseparation of the mercury. over the roughened surface of said chamber when tilted toward the open position.

hened surface of said chamber when trode sealed into said outer tube and communicating with the bore of the inner tube maar 'its center,` and sucient mercury contained within said tubes to connect the electrodes when the tube is in one position.

5. A mercurytube circuit contro/ller comprising a pair of concentrically fitted glass tubes, the outer one of which has a smooth bore and is sealed, and the inner one of which has a roughened bore and has an open end spaced away from a sealed `end of. the outer tube so asto leave an enlarged chamber .thereat, an electrode sealed into said chamber through-the outer tube, an electrode sealed into the outer tube near its center and communicating with the bore ot the inner tube, and mercurycontained within said tubes of suiiicientquantity to connect said electrodes when thetube is in a horizontalposition.

v6. A mercury tube switch comprising a cylindrical chamber of refractory material, a pair of axially spaced electrodes in said chamber,

chamber in suiiicient quantity to electrically connect said electrodes in oneposition of the chamber, the interior surface of the chamber having a varying degree of roughness whereby the true level of the mercury in said chamber is modified in a manner so as to cause the mercury to be drawn out into a stream of varying cross section` between said electrodes when the tube is tilted toward an open circuit position.

In witness whereof, I have hereunto set my hand this 13th day of Sept., 1923.

HENRYY E. WARREN.

mercury contained within said 

